The hydraulic architecture of Eucalyptus trees growing across a gradient of depth-to-groundwater

2015 ◽  
Vol 42 (9) ◽  
pp. 888 ◽  
Author(s):  
Sepideh Zolfaghar ◽  
Randol Villalobos-Vega ◽  
Melanie Zeppel ◽  
Derek Eamus
Keyword(s):  
Hydraulic Conductivity ◽  
Leaf Area ◽  
Water Availability ◽  
Safety Margin ◽  
Hydraulic Architecture ◽  
Sapwood Area ◽  
Huber Value ◽  
Xylem Vulnerability ◽  
Safety Margins ◽  
Hydraulic Safety

Heterogeneity in water availability acts as an important driver of variation in plant structure and function. Changes in hydraulic architecture represent a key mechanism by which adaptation to changes in water availability can be expressed in plants. The aim of this study was to investigate whether differences in depth-to-groundwater influence the hydraulic architecture of Eucalyptus trees in remnant woodlands within mesic environments. Hydraulic architecture of trees was examined in winter and summer by measuring the following traits: Huber value (HV: the ratio between sapwood area and leaf area), branch hydraulic conductivity (leaf and sapwood area specific), sapwood density, xylem vulnerability (P50 and Pe) and hydraulic safety margins across four sites where depth-to-groundwater ranged from 2.4 to 37.5 m. Huber value increased significantly as depth-to-groundwater increased. Neither sapwood density nor branch hydraulic conductivity (sapwood and leaf area specific) varied significantly across sites. Xylem vulnerability to embolism (represented by P50 and Pe) in both seasons was significantly and negatively correlated with depth-to-groundwater. Hydraulic safety margins increased with increasing depth-to-groundwater and therefore trees growing at sites with deeper water tables were less sensitive to drought induced embolism. These results showed plasticity in some, but not all, hydraulic traits (as reflected in HV, P50, Pe and hydraulic safety margin) in response to increase in depth-to-groundwater in a mesic environment.

scholarly journals Hydraulic architecture and water relations of several species at diverse sites around Sydney

2004 ◽  
Vol 52 (4) ◽  
pp. 509 ◽  
Author(s):  
Kate McClenahan ◽  
Catriona Macinnis-Ng ◽  
Derek Eamus
Keyword(s):  
Water Relations ◽  
Root Biomass ◽  
Woody Species ◽  
Leaf Water ◽  
Hydraulic Architecture ◽  
Evaporative Demand ◽  
Sapwood Area ◽  
Huber Value ◽  
Percentage Loss ◽  
Transverse Area

Seasonal comparisons of leaf water potential, root biomass, hydraulic architecture, xylem embolism and xylem dimensions were made for eight woody species in four diverse habitats (mangroves, coastal heathland, ridge-top woodland and river-flat woodland). In most comparisons, pre-dawn and minimum leaf water potentials were lower in winter than in summer, a result attributed to lower rainfall and a smaller root biomass in winter than in summer. Branch hydraulic conductivities (per unit transverse area, sapwood area or leaf area) were generally larger in summer than in winter across all species in all habitats. An inverse relationship between Huber value and conductivity was observed across all four habitats. Increased solar radiation and evaporative demand in the summer was associated with an increased percentage loss of xylem conductance arising from embolism, compared with winter. These results are discussed in the context of patterns and relationships among water relations, microclimate and hydraulic architecture.

Large branch and leaf hydraulic safety margins in subtropical evergreen broadleaved forest

2019 ◽  
Vol 39 (8) ◽  
pp. 1405-1415
Author(s):  
Shi-Dan Zhu ◽  
Rong-Hua Li ◽  
Peng-Cheng He ◽  
Zafar Siddiq ◽  
Kun-Fang Cao ◽  
...  
Keyword(s):  
Southern China ◽  
Woody Species ◽  
Atmospheric Temperature ◽  
Dry Season ◽  
Sapwood Area ◽  
Evergreen Broadleaved Forest ◽  
Safety Margins ◽  
Hot Dry Season ◽  
Hydraulic Safety ◽  
Dry Seasons

Abstract As a global biodiversity hotspot, the subtropical evergreen broadleaved forest (SEBF) in southern China is strongly influenced by the humid monsoon climate, with distinct hot-wet and cool-dry seasons. However, the hydraulic strategies of this forest are not well understood. Branch and leaf hydraulic safety margins (HSMbranch and HSMleaf, respectively), as well as seasonal changes in predawn and midday leaf water potential (Ψpd and Ψmd), stomatal conductance (Gs), leaf to sapwood area ratio (AL/AS) and turgor loss point (Ψtlp), were examined for woody species in a mature SEBF. For comparison, we compiled these traits of tropical dry forests (TDFs) and Mediterranean-type woodlands (MWs) from the literature because they experience a hot-dry season. We found that on average, SEBF showed larger HSMbranch and HSMleaf than TDF and MW. During the dry season, TDF and MW species displayed a significant decrease in Ψpd and Ψmd. However, SEBF species showed a slight decrease in Ψpd but an increase in Ψmd. Similar to TDF and MW species, Gs was substantially lower in the dry season for SEBF species, but this might be primarily because of the low atmospheric temperature (low vapor pressure deficit). On the other hand, AL/AS and Ψtlp were not significant different between seasons for any SEBF species. Most SEBF species had leaves that were more resistant to cavitation than branches. Additionally, species with stronger leaf-to-branch vulnerability segmentation tended to have smaller HSMleaf but larger HSMbranch. Our results suggest that SEBF is at low hydraulic risk under the current climate.

scholarly journals Coordination of leaf area, sapwood area and canopy conductance leads to species convergence of tree water use in a remnant evergreen woodland

2008 ◽  
Vol 56 (2) ◽  
pp. 97 ◽  
Author(s):  
Melanie Zeppel ◽  
Derek Eamus
Keyword(s):  
Leaf Area ◽  
Water Use ◽  
Canopy Conductance ◽  
Evaporative Demand ◽  
Sapwood Area ◽  
Huber Value ◽  
Tree Water Use ◽  
Decoupling Coefficient ◽  
The Relationship ◽  
Daily Total

This paper compares rates of tree water use, Huber value, canopy conductance and canopy decoupling of two disparate, co-occurring tree species, in a stand of remnant native vegetation in temperate Australia in order to compare their relative behaviour seasonally and during and after a drought. The study site was an open woodland dominated by Eucalyptus crebra F.Muell. (a broad-leaved species) and Callitris glaucophylla J.Thompson & L.A.S. Johnson (a needle-leaved tree species). Tree water use was measured with sapflow sensors and leaf area and sapwood area were measured destructively on felled trees. The Huber value was calculated as the ratio of sapwood area to leaf area. Diameter at breast height (DBH) of the stem was used as a measure of tree size. Canopy conductance was calculated with an inversion of the Penman–Monteith equation, whereas canopy decoupling) was calculated as described by Lu et al. (2003). The relationship between DBH and daily total water use varied during the four measurement periods, with largest rates of water use observed in summer 2003–2004, following a large rainfall event and the smallest maximum water use observed in winter 2003 when monthly rainfall was much less than the long-term mean for those months. Despite differences in the relationship between sapwood area and DBH for the two species, the relationship between daily total water use and DBH did not differ between species at any time. The same rates of water use for the two species across sampling periods arose through different mechanisms; the eucalypt underwent significant changes in leaf area whereas the Callitris displayed large changes in canopy conductance, such that tree water use remained the same for both species during the 2-year period. Canopy conductance and the decoupling coefficient were both significantly larger in winter than summer in both years. The generally low decoupling coefficient (0.05–0.34) reflects the low leaf area index of the site. When evaporative demand was small (winter), the degree of stomatal control was small and the decoupling coefficient was large. There was no relationship between tree size and either canopy conductance or the decoupling coefficient. Transpiration rates generally showed little variation between seasons and between species because of the balance between changes in leaf area, canopy conductance and evaporative demand. The occurrence of a significant drought did not appear to prevent these coordinated changes from occurring, with the result that convergence in water use was observed for these two disparate species.

scholarly journals Convergence in hydraulic architecture, water relations and primary productivity amongst habitats and across seasons in Sydney

2004 ◽  
Vol 31 (5) ◽  
pp. 429 ◽  
Author(s):  
Catriona Macinnis-Ng ◽  
Kate McClenahan ◽  
Derek Eamus
Keyword(s):  
Water Relations ◽  
Negative Correlation ◽  
Inverse Correlation ◽  
Leaf Traits ◽  
Significant Negative Correlation ◽  
Hydraulic Architecture ◽  
Xylem Embolism ◽  
Sapwood Area ◽  
Huber Value ◽  
The Cost

Convergence in leaf traits across biomes demonstrates generality in plant functioning. Relationships between hydraulic architecture and photosynthesis are less well studied. We investigated convergence in minimum leaf water potential (Ψmin), conductivity per sapwood area (ks), Huber value (Hv) and xylem embolism and photosynthesis in four habitats across two seasons (summer and winter) in the Sydney region in heathland, woodland (ridge-top), woodland (below-ridge) and mangrove. Seasonality strongly influenced all parameters in all habitats. Winter Ψmin values were lower than those for summer in the heathland and both woodland habitats but summer Ψmin values were lower than those for winter in the mangrove. Summer ks values were higher than winter values in all habitats, while Hv was higher in winter than summer for all habitats. Loss of conductance due to xylem embolism was larger in summer than winter in eight of 11 species. We also investigated relationships between the hydraulic parameters across habitats. There was a strong, significant inverse correlation between log-transformed Hv and log-transformed ks, which held across the seasons. There were significant inverse correlations between Ψmin and xylem embolism, which held within seasons but not across seasons. We found a strong, significant positive correlation between ks and Ψmin also within seasons but not across seasons and a significant negative correlation between xylem embolism and ks for winter but only a weak negative correlation between xylem embolism and ks for summer. We believe the seasonal patterns and relationships in hydraulic architecture and water relations are driven by the cost of efficient sapwood. This is demonstrated by the negative correlation between photosynthetic rate and ks in winter.

scholarly journals Water limitations on forest carbon cycling and conifer traits along a steep climatic gradient in the Cascade Mountains, Oregon

2015 ◽  
Vol 12 (22) ◽  
pp. 6617-6635 ◽  
Author(s):  
L. T. Berner ◽  
B. E. Law
Keyword(s):  
Carbon Cycling ◽  
Leaf Area ◽  
Wood Density ◽  
Water Availability ◽  
Radial Growth ◽  
Forest Carbon ◽  
Monthly Precipitation ◽  
Cascade Mountains ◽  
Average Growth ◽  
Sapwood Area

Abstract. Severe droughts occurred in the western United States during recent decades, and continued human greenhouse gas emissions are expected to exacerbate warming and drying in this region. We investigated the role of water availability in shaping forest carbon cycling and morphological traits in the eastern Cascade Mountains, Oregon, focusing on the transition from low-elevation, dry western juniper (Juniperus occidentalis) woodlands to higher-elevation, wetter ponderosa pine (Pinus ponderosa) and grand fir (Abies grandis) forests. We examined 12 sites in mature forests that spanned a 1300 mm yr−1 gradient in mean growing-year climate moisture index (CMIgy ), computed annually (1964 to 2013) as monthly precipitation minus reference evapotranspiration and summed October to September. Maximum leaf area, annual aboveground productivity, and aboveground live tree biomass increased with CMIgy (r2 = 0.67–0.88, P < 0.05), approximately 50-, 30-, and 10-fold along this drier to wetter gradient. Interannual fluctuations in CMI affected the annual radial growth of 91 % of juniper, 51 % of pine, and 12 % of fir individuals from 1964 to 2013. The magnitude of the site-average growth–CMI correlations decreased with increased CMIgy (r2 = 0.53, P < 0.05). All three species, particularly fir, experienced pronounced declines in radial growth from c. 1985 to 1994, coinciding with a period of sustained below-average CMIgy and extensive insect outbreak. Traits of stress-tolerant juniper included short stature, high wood density for cavitation resistance, and high investment in water transport relative to leaf area. Species occupying wetter areas invested more resources in height growth in response to competition for light relative to investment in hydraulic architecture. Consequently, maximum tree height, leaf area : sapwood area ratio, and stem wood density were all correlated with CMIgy . The tight coupling of forest carbon cycling and species traits with water availability suggests that warmer and drier conditions projected for the 21st century could have significant biogeochemical, ecological, and social consequences in the Pacific Northwest.

scholarly journals Large hydraulic safety margins protect Neotropical canopy rainforest tree species against hydraulic failure during drought

2019 ◽  
Vol 76 (4) ◽  
Author(s):  
Camille Ziegler ◽  
Sabrina Coste ◽  
Clément Stahl ◽  
Sylvain Delzon ◽  
Sébastien Levionnois ◽  
...  
Keyword(s):  
Tree Species ◽  
Turgor Loss Point ◽  
Canopy Tree ◽  
Hydraulic Failure ◽  
Xylem Vulnerability ◽  
Safety Margins ◽  
Hydraulic Safety ◽  
Dry Seasons ◽  
Canopy Tree Species ◽  
Embolism Resistance

Abstract Key message Abundant Neotropical canopy-tree species are more resistant to drought-induced branch embolism than what is currently admitted. Large hydraulic safety margins protect them from hydraulic failure under actual drought conditions. Context Xylem vulnerability to embolism, which is associated to survival under extreme drought conditions, is being increasingly studied in the tropics, but data on the risk of hydraulic failure for lowland Neotropical rainforest canopy-tree species, thought to be highly vulnerable, are lacking. Aims The purpose of this study was to gain more knowledge on species drought-resistance characteristics in branches and leaves and the risk of hydraulic failure of abundant rainforest canopy-tree species during the dry season. Methods We first assessed the range of branch xylem vulnerability to embolism using the flow-centrifuge technique on 1-m-long sun-exposed branches and evaluated hydraulic safety margins with leaf turgor loss point and midday water potential during normal- and severe-intensity dry seasons for a large set of Amazonian rainforest canopy-tree species. Results Tree species exhibited a broad range of embolism resistance, with the pressure threshold inducing 50% loss of branch hydraulic conductivity varying from − 1.86 to − 7.63 MPa. Conversely, we found low variability in leaf turgor loss point and dry season midday leaf water potential, and mostly large, positive hydraulic safety margins. Conclusions Rainforest canopy-tree species growing under elevated mean annual precipitation can have high resistance to embolism and are more resistant than what was previously thought. Thanks to early leaf turgor loss and high embolism resistance, most species have a low risk of hydraulic failure and are well able to withstand normal and even severe dry seasons.

Xylem' Structure and Water Conduction in Conifer Trees, Dicot Trees, and Llanas

IAWA Journal ◽  
1985 ◽  
Vol 6 (4) ◽  
pp. 309-317 ◽  
Author(s):  
Frank W. Ewers
Keyword(s):  
Hydraulic Conductivity ◽  
Specific Conductivity ◽  
Glass Capillary ◽  
Pressure Potential ◽  
Sapwood Area ◽  
Woody Vines ◽  
Xylem Structure ◽  
Huber Value ◽  
Water Conduction ◽  
And Function

Coniferous trees, dicotyledonous trees, and dicotyledonous lianas (woody vines) form interesting morphological contrasts in their xylem structure and function. Lianas have among the largest (up to 8 metres or more) and widest (up to 500 µm) vessels in the plant kingdom. In conifers the water transport occurs through tracheids, which are relatively inefficient in transport. We can compare disparate growth forms in terms of leaf-specific. conductivity (LSC), which is hydraulic conductivity per surface area of leaves supplied by a stem. LSC is inversely proportional to localised pressure potential gradients. LSC is equal to the Huber value (sapwood area per leaf area supplied) times the specific conductivity (hydraulic conductivity per sapwood area). Lianas are similar to dicot trees and conifers in having hydraulic constrictions (low LSCs) at branch junctions. However, lianas generally have greater LSCs and specific conductivities but lower Huber values than do conifers. Dicot trees are intermediate in these values. The narrow but efficient stems of lianas are possible partly because lianas are not self-supporting; the mechanical requirements are reduced. Secondly, the wide and efficient vessels of lianas remain conductive for much longer than might be expected (two to several years, versus one year for similar wide vessels in dicots). Based upon experiments with glass capillary tubes and with living stem tissue, larger vessels are more susceptible to freezinginduced embolism than are small ones. However, in lianas, root pressures might serve to refill cavitated vessels on a daily or seasonal basis.

scholarly journals Hydraulic Traits Performances of Three Pine Species in Tunisia

2019 ◽  
Vol 11 (13) ◽  
pp. 20
Author(s):  
Sameh Cherif ◽  
Olfa Ezzine ◽  
Mohamed Larbi Khouja ◽  
Zouhaier Nasr
Keyword(s):  
Hydraulic Conductivity ◽  
Water Potential ◽  
Mediterranean Forests ◽  
Stem Water Potential ◽  
Humid Climate ◽  
Safety Margins ◽  
Hydraulic Safety ◽  
The Impact ◽  
Semi Arid ◽  
Pine Species

Mediterranean forests including Tunisian pine species are threatened by the rising of temperature and decreasing of precipitation. The impact of the increase of aridity differs across species depending on their stomatal and hydraulic responses. In this paper, three pine species: P. halepensis, P. brutia and P. canariensis growing in three different climatic zones: humid, sub-humid and semi-arid, were studied to detect their different responses to drought and guide their selection for reforestation program. Measurements carried out are hydraulic conductivity at point P50, specific conductivity (Ks), midday stem water potential and hydraulic safety margins. Results showed that during summer, vulnerability to embolism, estimated by water potential inducing 50% loss of xylem hydraulic conductivity (P50), is strongly associated with the capacity for drought resistance. Pinus halepensis (P50 = -4.19 MPa) was found to be more resistant to drought than P. brutia and P. canariensis in the semi-arid climate, whereas P. brutia tolerated the humid climate (P50 = -3.7 MPa) and P. canariensis seems more adapted to the sub-humid climate (P50 = -4.08 MPa). Hydraulic safety margins confirmed the conservative behavior of pine species to avoid drought and for maintaining relatively high water potential in dry conditions. These findings help to assess the impact of mid-summer water deficit on pine species in the context of climate change and to select among these species the most resistant for future reforestation programs.

scholarly journals Bootstrap and Order Statistics for Quantifying Thermal-Hydraulic Code Uncertainties in the Estimation of Safety Margins

2008 ◽  
Vol 2008 ◽  
pp. 1-9 ◽  
Author(s):  
Enrico Zio ◽  
Francesco Di Maio
Keyword(s):  
Confidence Interval ◽  
Order Statistics ◽  
Nuclear Reactor ◽  
Safety Margin ◽  
Fuel Cladding ◽  
Complete Group ◽  
Bootstrap Technique ◽  
Safety Margins ◽  
Group Distribution

In the present work, the uncertainties affecting the safety margins estimated from thermal-hydraulic code calculations are captured quantitatively by resorting to the order statistics and the bootstrap technique. The proposed framework of analysis is applied to the estimation of the safety margin, with its confidence interval, of the maximum fuel cladding temperature reached during a complete group distribution blockage scenario in a RBMK-1500 nuclear reactor.

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